Description of Data
Data files suitable for importing into the Forestry-oriented Linear Programming Interpreter (FOLPI) (García, 1984; Manley et al, 1991) modelling system were generated from the 1999 NEFD database. The 1999 NEFD database is made up of planted forest area data as reported in A National Exotic Forest Description as at 1 April 1999 (Ministry of Agriculture and Forestry, 2000) and yield data as reported in the National Exotic Forest Description Regional Yield Tables as at 1 April 1995 (Ministry of Forestry, 1996).
Separate FOLPI data files were generated for each NEFD crop type present in each of the ten wood supply regions. Eight primary crop types were used:
• radiata pine pruned with production thinning
• radiata pine pruned without production thinning
• radiata pine unpruned with production thinning
• radiata pine unpruned without production thinning
• Douglas-fir with production thinning
• Douglas-fir without production thinning
• other softwoods
• hardwoods.
For further definitions of the crop types see appendix 1.
In five wood supply regions, the primary radiata pine crop types were split into two on the basis of year of planting. This was introduced into the modelling in an attempt to capture some of the changes that have occurred over time in forest management and in the growth rate and quality of radiata pine. Stands planted before 1976 and stands planted from 1976 on were separated into two new crop types. A unique yield table was developed for each new crop type reflecting these changes.
The five wood supply regions where this age-based separation has been used are:
• Central North Island
• East Coast
• Hawkes Bay
• Nelson & Marlborough
• Otago & Southland.
Further details about separating the primary radiata pine crop types are available in the National Exotic Forest Description Regional Yield Tables as at 1 April 1995 (Ministry of Forestry, 1996).
The hardwood resource was separated into two croptypes in the Central North Island and Otago & Southland regions. This separation was based on management objectives. Each of these regions has approximately ten thousand hectares of hardwoods growing on short rotations for wood fibre production. In order to incorporate the different rotation lengths and yields a separate crop type was created for the short rotation hardwoods. Only the combined hardwood (short rotation and long rotation) results are presented in this report in order to preserve the confidentiality of the short rotation hardwood results. The short rotation hardwoods are owned by two companies, one based in the Central North Island and the other in Southland.
The broadly defined crop types used in the NEFD means that stands that have been allocated to the same crop type may in fact still be significantly different in terms of total recoverable volumes and volume by log type.
The yield tables used in these forecasts apportion total recoverable volumes into three log types:
• pruned logs
• unpruned logs
• pulp logs
as outlined in table 5.
Table 5: Radiata Pine Log Type Specifications
| Log grade | Small end diameter (s.e.d.) (cm) |
Diameter of largest branch (cm) |
Sweep class 1 number |
|---|---|---|---|
| Pruned logs 2 | |||
| Unpruned logs | |||
| Pulp logs |
Note:
1. Sweep class is defined as the maximum deviation from straightness along the length of
the log. For the technical definition of sweep class refer to Whiteside and Manley, 1987.
In general terms:
•
sweep class 1 is deemed suitable for sawlogs and veneer
• sweep class 2 is deemed unsuitable for
sawlogs and veneer.
2. For the Central North Island, East Coast, and Hawkes
Bay wood supply regions, a 35-centimetre s.e.d. was used for pruned logs.
Further details about the log type specification are available in the National Exotic Forest Description Regional Yield Tables as at 1 April 1995 (Ministry of Forestry, 1996).
All model simulations were started with the net stocked area as at 1 April 1999. For the first two years of the model runs, the Ministry of Agriculture and Forestry's best estimates of actual new planting and restocking were added. In addition, estimates of harvesting for this same two-year period were included in the model. Tables 6 and 7 show the estimated areas of new planting, restocking and harvesting included in the model simulations for the years ended 31 March 2000 and 2001 respectively.
Table 6: New Planting, Restocking and Harvesting for the Year Ended 31 March 2000 (hectares)
| Area as at | New Planting | Restocking | Harvesting | Area as at | ||||||||||
| 1 April | + | ye 31 March | + | ye 31 March | - | ye 31 March | = | 1 April Region | ||||||
| 1999 | 2000 | 2000 | 2000 | 2000 | ||||||||||
| Northland | 199 243 | 2 290 | 1 966 | 2 127 | 201 372 | |||||||||
| Auckland | 53 414 | 458 | 826 | 1 181 | 53 517 | |||||||||
| Central North Island | 569 355 | 3 435 | 13 474 | 19 169 | 567 095 | |||||||||
| East Coast | 143 623 | 3 435 | 618 | 1 221 | 146 455 | |||||||||
| Hawkes Bay | 120 771 | 2 290 | 1 372 | 1 410 | 123 023 | |||||||||
| Southern North Is | 147 132 | 3 435 | 739 | 1 138 | 150 168 | |||||||||
| Nelson & Marlborough | 172 490 | 1 603 | 4 137 | 2 873 | 175 357 | |||||||||
| West Coast | 33 278 | 229 | 591 | 454 | 33 644 | |||||||||
| Canterbury | 112 332 | 1 717 | 1 665 | 1 104 | 114 610 | |||||||||
| Otago & Southland | 179 127 | 4 008 | 2 039 | 3 323 | 181 851 | |||||||||
| New Zealand total | 1 730 765 | 22 900 | 27 427 | 34 000 | 1 747 092 | |||||||||
Table 7: New Planting, Restocking and Harvesting for the Year Ended 31 March 2001 (hectares)
| Area as at | New Planting | Restocking | Harvesting | Area as at | ||||||||||
| 1 April | + | ye 31 March | + | ye 31 March | - | ye 31 March | = | 1 April | ||||||
| Region | 2000 | 2001 | 2001 | 2001 | 2001 | |||||||||
| Auckland | 53 517 | 600 | 1 181 | 1 216 | 54 082 | |||||||||
| Central North Island | 567 095 | 4 500 | 19 169 | 19 733 | 571 031 | |||||||||
| East Coast | 146 455 | 4 500 | 1 221 | 1 257 | 150 919 | |||||||||
| Hawkes Bay | 123 023 | 3 000 | 1 410 | 1 452 | 125 981 | |||||||||
| Southern North Island | 150 168 | 4 500 | 1 138 | 1 171 | 154 635 | |||||||||
| Nelson & Marlborough | 175 357 | 2 100 | 2 873 | 2 958 | 177 372 | |||||||||
| West Coast | 33 644 | 300 | 454 | 467 | 33 931 | |||||||||
| Canterbury | 114 610 | 2 250 | 1 104 | 1 136 | 116 828 | |||||||||
| Otago & Southland | 181 851 | 5 250 | 3 323 | 3 421 | 187 003 | |||||||||
| New Zealand total | 1 747 092 | 30 000 | 34 000 | 35 000 | 1 776 092 | |||||||||
